[ContentIndex] Check SW reg execution context before using it

The crash report seems to imply that this can be null, although I'm
still unsure when that would happen.

Bug: 1150628, 1143619
Change-Id: Ifceb52846deaab48ec749ee11992b3c586ecbcb5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2550182
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Reviewed-by: Richard Knoll <knollr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829267}

third_party/blink/renderer/modules/content_index/content_index.cc

@@ -118,14 +118,22 @@ void ContentIndex::DidGetIconSizes(
     ScriptPromiseResolver* resolver,
     mojom::blink::ContentDescriptionPtr description,
     const Vector<gfx::Size>& icon_sizes) {
+  ScriptState* script_state = resolver->GetScriptState();
+  ScriptState::Scope scope(script_state);
+
   if (!icon_sizes.IsEmpty() && description->icons.IsEmpty()) {
-    ScriptState* script_state = resolver->GetScriptState();
-    ScriptState::Scope scope(script_state);
     resolver->Reject(V8ThrowException::CreateTypeError(
         script_state->GetIsolate(), "icons must be provided"));
     return;
   }
 
+  if (!registration_->GetExecutionContext()) {
+    // The SW execution context is not valid for some reason. Bail out.
+    resolver->Reject(V8ThrowException::CreateTypeError(
+        script_state->GetIsolate(), "Service worker is no longer valid."));
+    return;
+  }
+
   if (icon_sizes.IsEmpty()) {
     DidGetIcons(resolver, std::move(description), /* icons= */ {});
     return;
@@ -152,6 +160,13 @@ void ContentIndex::DidGetIcons(ScriptPromiseResolver* resolver,
     }
   }
 
+  if (!registration_->GetExecutionContext()) {
+    // The SW execution context is not valid for some reason. Bail out.
+    resolver->Reject(V8ThrowException::CreateTypeError(
+        script_state->GetIsolate(), "Service worker is no longer valid."));
+    return;
+  }
+
   KURL launch_url = registration_->GetExecutionContext()->CompleteURL(
       description->launch_url);